This invention relates to a novel liquid crystal substance having a positive dielectric anisotropy.
Liquid crystal display elements utilize optical anisotropy and dielectric anisotropy of liquid crystal substances, and are classified by their display modes into various types such as TN type (twisted nematic type), DS type (dynamic scattering type), guest-host type, DAP type, etc.; and the properties of liquid crystal substances suitable to their respective uses are different. However, it is common to any of such liquid crystal substances that they must to be stable to moisture, air, heat, light, etc., and also, there is a need for those which exhibit a liquid crystal phase within as broad a temperature range as possible, centering at room temperature. However, no single compounds satisfying such requirements have been found to date, and it is the present status that liquid crystal compositions obtained by mixing together several kinds of liquid crystal compounds and non-liquid crystal compounds have been used. In particular, liquid crystal display elements actuated within a temperature range as broad as -30.degree. to +100.degree. C. have come to be required. In order to satisfy such requirements, it is effective to reduce their viscosities, particularly those at lower temperatures. Generally, however, those having a higher transparent point (N-I point) have higher viscosity, while those having a lower viscosity such as alkylphenylcyclohexane derivatives have a lower transparent point.
Thus, the object of the present invention is to provide novel liquid crystal compounds which have a higher transparent point in spite of their lower viscosity and also have a broad nematic temperature range, and liquid crystal compositions containing the same.